As to Count III.
III. A person is able, while he obeys a divine prohibition, to sin against God by that very act of obedience.
– Open Letter to Bishops of the Catholic Church, Easter Week, 2019
FUNDAMENTALS OF CATHOLIC DOGMA, Ludwig Ott > INTRODUCTION > §6. catholic Truths > p.9:
2. Dogmatic Facts (facta dogmatica)
[…] The fact that a defined text does or does not agree with the doctrine of the Catholic Faith is also, in a narrower sense, a “dogmatic fact.” […]
392. What is sin?
Sin is “a word, an act, or a desire contrary to the eternal Law” (Saint Augustine). It is an offense against God in disobedience to his love. It wounds human nature and injures human solidarity. Christ in his passion fully revealed the seriousness of sin and overcame it with his mercy. [Cf. CCC 1850 & 1871]
Therefore, count III. is a false proposition (propositio falsa), a proposition contrary to a dogmatic fact which in this case is ‘what sin is’.